Significant mortality of eggs and young larvae of two pine processionary moth species due to the entomopathogenic fungus <italic>Metarhizium brunneum</italic>.

Bioassays were conducted to determine the susceptibility of egg masses and young larvae of two pine processionary moth species, <italic>Thaumetopoea pityocampa</italic> and <italic>Thaumetopoea wilkinsoni</italic>, to two strains (ARSEF4556, V275) of the entomopathogenic fungus <italic>Metarhizium brunneum</italic>. Mortality of treated eggs by both strains ranged from 96% to 99% but not all of this was caused by <italic>M. brunneum</italic> since control groups also experienced egg mortality due to saprophytic fungi. Still, larvae hatched in the laboratory from eggs treated with <italic>M. brunneum</italic> were all killed by this fungus, acquiring <italic>M. brunneum</italic> conidia, whereas larval mortality was 0% in the control groups. Young larvae of both pine processionary moth species were also highly susceptible to ARSEF4556 and V275 with larval mortality ranging between 94% and 100%, 8 days post-inoculation, with the vast majority of larvae being killed within the first 2-4 days. Larval mortality was dose dependent. Results were consistent across the two pine processionary moth species, showing that the pathogenicity of <italic>M. brunneum</italic> to both eggs and young larvae might be promising for biological control of these insect pests. The study also showed that non-target parasitoids of pine processionary moth eggs were also susceptible to <italic>M. brunneum</italic>. Further work is required to understand and reduce the <italic>M. brunneum</italic> effect on non-target insects. [ABSTRACT FROM AUTHOR]